problem with fax t38 protocol

[erodrig]

hi

i have an mpls nework with equipment cisco 2821, 2901 and 2801, and i have problems with fax calls, i configured the fax protocol t38 in all routers but when i want to send a fax to the 2821 equipment from either 2801 and 2901, the protocol t38 is not working and the fax call use cisco protocol (although t38 is configured in all routers). the calls betwen 2801 and 2901 works ok, and from 2821 to 2801/2901 works ok too.

any idea of whats happens? do you think is a problem of ios version?

these are de ios version

2821 .-c2800nm-spservicesk9-mz.124-3i.bin

2801 .- c2801-spservicesk9-mz.150-1.M6.bin

2901 .-c2900-universalk9-mz.SPA.150-1.M7.bin

[Maxim Denisov]

Hi,

How have you configured t.38? What protocol are you using? Check the voice service voip and your dial-peers for the fax relay config.

Just interesting why do you want using t.38 if all devices support cisco fax relay? My personal experience syay that cisco fax relay is most reliable, especialy on losy links.

Sent from Cisco Technical Support iPad App

[erodrig]

hi

this is the configuration on the 2821:

voice service voip

fax protocol t38 ls-redundancy 0 hs-redundancy 0 fallback cisco

dial-peer voice 10037 voip

description CONEXION CELAYA DISTRITO XV

destination-pattern 561.

session target ipv4:172.16.200.37

incoming called-number .

dtmf-relay h245-alphanumeric

codec g729r8 bytes 50

fax protocol t38 ls-redundancy 0 hs-redundancy 0 fallback cisco

ip qos dscp ef signaling

no vad

this is the configuration on 2801

voice service voip

fax protocol t38 ls-redundancy 0 hs-redundancy 0 fallback cisco

dial-peer voice 10016 voip

description CONEXION VOZ A FAXES

destination-pattern 300[1-6,8]

session target ipv4:172.1.1.51

incoming called-number .

dtmf-relay h245-alphanumeric

codec g729r8 bytes 50

fax protocol t38 ls-redundancy 0 hs-redundancy 0 fallback cisco

ip qos dscp ef signaling

no vad

i want to use T38 because the bandwidth of the fax call is 16K, if i use cisco protocol the bandwidth reaches up 24k, and the router start to drop voice packets

thanks

[Daniele Giordano]

Try to add the command "fax rate xxx" to dial-peers.

If it doesn't work debug the call negotiation with commands

debug vtsp all command output

debug fax relay t30

and post the output.

Regards.